State-of -the-art digital imaging and processing technologies are applied to Fiber-Optic-Transillumination to achieve its full potential for the safe, cost-effective diagnosis and treatment of dental caries. The Phase 1 laboratory version of EOS's Digital Imaging Fiber Optic Transillumination (DIFOTT) device provides significant improvements to conventional transillumination. A monitor displays DIFOTT images, analyzed in real time, enabling dentists to: (acquire images under controlled, repeatable conditions; select digital image analysis methods, e.g. contrast enhancement between carious and sound tissue) DIFOTT provides significant information not available by X-ray, and likely to be missed by conventional transillumination without computer-assisted analysis. In Phase 2, (the reliability of DIFOTT will be examined, through tests in vitro and in vivo, for detection of frank, incipient and recurrent caries, on or near approximal, smooth, occlusal and/or root surfaces. ROC analyses will employ histology as the "gold standard.") Three clinical prototypes will be built, and evaluated at three clinical centers. The prototype will have a hand held probe, a fiber-optic coupled halogen light source to illuminate the tooth, and a solid-state imager. The attached computer (PC) provides image processing that facilitates both detection of incipient caries and monitoring of changes. PROPOSED COMMERCIAL APPLICATION Potentially standard tool for safe, rapid, accurate computer-aided diagnosis and monitoring of caries by the average dental clinician, at costs comparable to radiography, and augmenting techniques. The domestic market for the device in Phase 3 consists of all 150,000+ dentists actively in practice in the US. In addition a substantial number of sales to dentists outside the US is expected.